Aug
14
SETI and the Fermi Paradox
“Here [pointing to new, blown-up photo from Voyager] is the Earth in a sunbeam. And you can see it; it is in fact less than a pixel in size. And, uh, this is where we live — on a blue dot. There is no evidence suggesting life anywhere else. For me, that underscores the rarity and preciousness of the Earth and the life upon it.” — Carl Sagan (NASA HQ Voyager Press Conference, June 6, 1990)
With all the recent talk and renewed(?) interest in UFOs and the search for extraterrestrial intelligence (SETI), I thought it might be good to review a couple notable… er, I’m not sure if there’s a word that lumps them together. The one I’ll address here is an observation via question, along with attempts to respond. The other is a formula proposed to shed light on the probabilities involved.
Back in 1950, Enrico Fermi worked with Emil Konopinski, Edward Teller, and Herbert York at Los Alamos National Laboratory in New Mexico. One summer day they were discussing flying saucers while walking to lunch. By the time they sat down to eat, the discussion had moved on, but Fermi suddenly blurted out some variation of “But where is everybody?” As Teller recalled decades later,
“The result of his question was general laughter because of the strange fact that in spite of Fermi’s question coming from the clear blue, everybody around the table seemed to understand at once that he was talking about extraterrestrial life.”
York remembered that Fermi “followed up with a series of calculations on the probability of earthlike planets, the probability of life given an earth, the probability of humans given life, the likely rise and duration of high technology, and so on. He concluded on the basis of such calculations that we ought to have been visited long ago and many times over.”
Fermi died of cancer in 1954, but the problem, known as “The Fermi Paradox”, has vexed physicists and others ever since. (And probably before, since Fermi was not the first to mention the problem.) A few have attempted to address the question in print, either in an academic journal (e.g., astrophysicist Michael H. Hart in a 1975 issue of the Quarterly Journal of the Royal Astronomical Society; planetary scientist S. Alan Stern in the AAS/Division for Planetary Sciences Meeting Abstracts #49 (Oct. 2017)) or in popular book form (e.g., The Fermi Paradox: Where are all the Aliens? (2020) by Alexander Bostic; a section of End Times (2019) by science writer Bryan Walsh).
Theoretical physicist Stephen Webb published If the Universe Is Teeming with Aliens … WHERE IS EVERYBODY?: Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life in 2002. In 2015 he published a second edition, which expanded it to 75 possible solutions. (In case you’re wondering, no, I don’t have a copy,… yet.)
Fermi’s question is often stated with a bit more detail these days to reflect current understandings of — or, at least, observational data and theoretical conjectures about — the universe. So, for example, from Webb’s book:
“Given the fact that there are perhaps 400 billion stars in our Galaxy alone, and perhaps 400 billion galaxies in the Universe, it stands to reason that somewhere out there, in the 14-billion-year-old cosmos, there is or once was a civilization at least as advanced as our own. The sheer enormity of the numbers almost demands that we accept the truth of this hypothesis. Why, then, have we encountered no evidence, no messages, no artifacts of these extraterrestrials?”
The following from Wikipedia (though it may have originated elsewhere) is a helpful organization of proposed solutions to the Fermi Paradox:
Rarity of intelligent life
o Extraterrestrial life is rare or non-existent
o Extraterrestrial intelligence is rare or non-existent
o Periodic extinction by natural events
Evolutionary explanations
o Intelligent alien species have not developed advanced technologies
o It is the nature of intelligent life to destroy itself
o It is the nature of intelligent life to destroy others
o Civilizations only broadcast detectable signals for a brief period of time
o Alien life may be too alien
Sociological explanations
o Colonization is not the cosmic norm
o Alien species may have only settled part of the galaxy
o Alien species may not live on planets
o Alien species may isolate themselves from the outside world
Economic explanations
o Lack of resources needed to physically spread throughout the galaxy
o It is cheaper to transfer information than explore physically
Discovery of extraterrestrial life is too difficult
o Humans have not listened properly
o Humans have not listened for long enough
o Intelligent life may be too far away
o Intelligent life may exist hidden from view
Willingness to communicate
o Everyone is listening but no one is transmitting
o Communication is dangerous
o Earth is deliberately avoided
o Earth is deliberately isolated (planetarium hypothesis)
Alien life is already here unacknowledged
This system probably covers most proposals but not all. For example, it would seem to be missing a section for “Technological shortcomings”, which would include things like “Humans haven’t pointed our telescopes at the right sections of the sky” (though that might be covered under “Alien species may have only settled part of the galaxy”) and “Human technology isn’t yet advanced enough to detect transmissions from alien civilizations” (a corollary to “Intelligent alien species have not developed advanced technologies”).
In my follow-up to this article, we’ll look at the Drake Equation, an attempt to formalize a formula (say that 10x fast!) for calculating the probability of the existence of alien civilizations.
